Microwatt MOSLED Using ${\hbox {SiO}}_{\rm x}$ With Buried Si Nanocrystals on Si Nano-Pillar Array

Microwatt light emission from a metal-oxide-semiconductor light-emitting diode (MOSLED) made by using SiOx film with buried Si nanocrystals on Si nano-pillar array is demonstrated. The Si nano-pillar array obtained by drying the rapidly self-aggregated Ni nano-dot-masked Si substrate exhibit size, aspect ratio, and density of 30 nm, 10, and 2.8times10¹⁰ cm^-2, respectively. These high-aspect-ratio Si nano-pillar array helps to enhance the Fowler-Nordheim tunneling-based carrier injection and to facilitate the complete relaxation on total internal reflection, thus increasing the quantum efficiency by one order of magnitude and improving the light extraction from the nano-roughened device surface by three times at least. The light-emission intensity, turn-on current and power-current slope of the MOSLED are 0.2 mW/cm² , 20-30 muA, and 3plusmn0.5 mW/A, respectively. At a biased current of 400 muA, the highest external quantum efficiency is over 0.2% to obtain the maximum EL power of > 1 muW. Compared with the same device made on smooth Si substrate under a power conversion ratio of 1 times 10^-4 , such an output power performance is enhanced by at least one order of magnitude.